1. Field of the Invention
Example embodiments generally relate to an optical scanner and an image forming apparatus incorporating the optical scanner, for example, for easily replacing a light source and efficiently adjusting a beam pitch.
2. Description of the Related Art
Image forming apparatuses, such as copiers, facsimile machines, printers, and multifunction devices having at least one of copying, printing, scanning, and facsimile functions, typically form a toner image on a recording medium (e.g., a transfer sheet) based on image data using one of several electrophotographic methods.
Thus, for example, a charging device charges a surface of a photoconductor, serving as a latent image carrier. An optical scanner emits a light beam onto the charged surface of the photoconductor to form an electrostatic latent image on the photoconductor according to the image data. A development device develops the electrostatic latent image with a developer (e.g., toner) into a visible toner image. After a transfer device transfers the toner image onto a transfer sheet, the toner image is fixed on the transfer sheet by heat and pressure applied by a fixing device, thereby forming the toner image on the transfer sheet.
Typically, optical scanners use a laser diode (LD) as a light source for emitting the light beam. The light beam emitted from the LD is formed into a predetermined shape via a collimate lens and an aperture, and directed onto a polygon mirror that then deflects the light beam to form an image on a surface of a photoconductor.
One known related-art optical scanner includes a holder for holding the light source. The light source is inserted into a light source mounting portion of the holder, thereby limiting its susceptibility to environmental changes such as temperature changes.
However, when a failure occurs in the light source, the light source needs to be removed from the light source mounting portion. Care must be taken with its removal, however, if a user pulls out the light source from the holder with too much force, the light source mounting portion may be damaged.
Moreover, since the LD as a light source has a vertical divergence angle different from a lateral divergence angle, the light beam emitted by the LD has an elliptical shape. Thus, in order to form the light beam after passing through the aperture into a desired shape, a major axis of the elliptical light beam needs to correspond to the orientation of the aperture split. However, the LD cannot rotate after being mounted in the light source mounting portion by press-fitting. Therefore, when the major axis of the light beam deviates from the orientation of the slit of the aperture, the light beam cannot be formed into the desired shape.
Another related-art optical scanner uses a multi-beam scanning method, which uses a laser diode array (LDA) including a plurality of light-emitting points as light sources arranged in array. In order to obtain a desired beam pitch, the light source needs to be attached to the light source mounting portion after defining a position of the light source in a rotational direction. However, the light source cannot rotate once it is mounted in the mounting portion, and thus the beam pitch cannot be adjusted.
If the holder holding the light source is rotatably attached to a housing so as to rotate independently from the housing, the position of the light source in a rotational direction can be adjusted, thereby making the beam pitch adjustable. However, provision of such a rotatable holder increases the number of components and thus the cost of the apparatus.
Accordingly, there is a need for a technology capable of easily attaching and removing a light source and efficiently adjusting a beam pitch after attachment of the light source while reducing the number of components.